Method and a device for the underwater construction of concrete structures

ABSTRACT

A flexible and leak-tight jacket having an internal space which corresponds to the casting space of the underwater structure is placed in position at the construction site, at least part of the internal space is filled with liquid ballast in order to subject the jacket walls to a pressure which is higher than the ambient hydrostatic pressure, and concrete or hardenable material is finally poured into the jacket while the liquid ballast is discharged.

United States Patent Pochitaloff-Huvale et al. July 8, 1975 METHOD AND A DEVICE FOR THE 1,197,225 9/1916 Moorhead 249/1 0? 2,591,625 4/1952 511110088011 52/727 X 3,314,239 4/1967 Baron et a1, 6!}46 CONCRETE STRUCTURES 3,524,320 8/1970 Turzillo 61/38 [75] Inventors: Leonid Pochitalofi-Huvale; 3,555,751 l/l97i Thorgusen 52/]69 Alexandre Domboy, both of Paris France FOREIGN PATENTS OR APPLICATIONS 809.856 12/l936 France 249/144 [73] Asslgnee- Pmhmhmmvale, Pam 975,475 11/1964 United Kingdom 61/46 [22] Filed: June 1973 Primary ExaminerJacob Shapiro 2 APPL 374 50 Attorney, Agent, or FirmYoung & Thompson [30] Foreign Application Priority Data 57 ABSTRACT uy rance A flexlble and leak-tight acket havmg an Internal 52 us. (:1. 61/46 61/43- 61/465 which cmmspmds Casting 61/72 249/3 underwater structure is placed in position at the con- [SI] 1m. Cl i i I 5 Eozd 29/00 struction site, at least part of the internal space is [58] Field 'gg 6H43 46 5 50 63 filled with liquid ballast in order to subject the jacket 6H69 721 2419/1 1 walls to a pressure which is higher than the ambient 9 3 2 425 hydrostatic pressure, and concrete or hardenable material is finally poured into the jacket while the liquid [56] References Cited ballast is discharged.

UNITED STATES PATENTS 25 Claims, 31 Drawing Figures 629.135 7/1899 Nixon et a1. 61/43 d Zc I n T i 1 SHEET PATENTED JUL 81975 PATENTED L 3 SHEET PATENTEUJIJL 8 ms SHEET Fig.25

1 METHOD AND A DEVICE FOR THE UNDERWATER CONSTRUCTION OF CONCRETE STRUCTURES This invention relates to a method for building underwater concrete structures as well as a device which is primarily intended to carry the method into practical effect. The invention is also concerned with the totally or partially immersed structures which are thus formed.

It is known that the construction of underwater structures presents major problems which are in turn liable to be attended by serious consequences both in regard to time taken for completion and capital cost of structuresv Various artificial and often very laborious expedients are in fact adopted in an effort to ensure that the project site and construction personnel are governed by conditions which are comparable with those prevailing in open-air operations.

In particular, one known practice consists in the use of temporary dams, boreholes, cofferdams or compressed-air caissons for work under the sea, on lake and river beds or on swamp sites. Any one of these methods can be employed as a function in particular of the scope of the work and the depth of immersion of the finished structure. But this carries heavy penalties such as slow execution of work, high capital cost and even exposure of personnel to serious health hazards in the case of compressed-air caissons.

The aim ofthe present invention is to overcome these disadvantages by virtue ofa method whereby underwater structures can be built entirely from the surface by adopting general means which are appreciably reduced in comparison with those of conventional methods. It is a primary objective of the invention to reduce the amount of time allotted for a project, in particular for underwater structures of substantial length such as tunnels under the sea.

There are also other known methods entailing the use of prefabricated elements which are transported to the construction site in order to be lowered underwater and assembled together in different ways. In comparison with these methods, the present invention again provides a considerable improvement by permitting a reduction of the masses to be supported and displaced inasmuch as the immersed unit weight of structural sections and components can be varied as required by the building contractors or even practically reduced to zero.

In accordance with the invention, the method for building at least partially immersed structures by pouring concrete or any like hardenable material is characterized in that a flexible and leak-tight jacket is placed in position at the intended location, that at least part of the internal space of said jacket is filled with a liquid ballast having the design function of applying to the jacket walls a pressure which is higher than the ambient hydrostatic pressure, that the internal space of the jacket which is thus filled corresponds substantially to the casting space of the structure to be built, and that the concrete or like hardenable material is then poured into the jacket while discharging the liquid ballast which had been present therein.

This method makes it possible to form massive structures if a single-walled jacket is employed and hollow structures if said jacket has a double wall, in which case the intermediate space corresponds substantially to the casting space. The arrangement of the jacket differs to a substantial extent according as the structure to be built is intended to project above the surface of the water or to be immersed to a small depth or whether it is intended on the contrary to be immersed to a substantial depth and even embedded in the bottom.

In the case of a structure which projects above the surface or is immersed to a small depth, an opentopped jacket in free communication with the atmosphere is employed. On the contrary, in the case of work carried out below a certain depth, it is an advantage to make use of a closed jacket for circulating liquid from the surface in the flow motions which are necessary for the formation of the structure and which can be carried out from a workshop-vessel by means of a pump, for example.

In accordance with a further property of the invention, the device which is mainly intended for the application of the method of building at least partially immersed structures is characterized in that it comprises a flexible and leak-tight jacket so arranged as to be filled at least partially with a liquid ballast which subjects the walls to a pressure of higher value than the ambient hydrostatic pressure, the internal space of the jacket which is thus filled being such as to correspond substantially to the casting space of the structure to be built, said jacket being so arranged as to be subsequently filled with concrete or like hardenable material and to permit the discharge of the liquid ballast which has thus been replaced.

In one advantageous embodiment of the invention, the wall of the jacket is associated with a rigid reinforcement system which has the effect of maintaining substantially constant the shape of the jacket which has thus been stiffened.

In particular, said reinforcement system can comprise both elements which are integrated with the jacket wall and internal elements which are located within the casting space. Said internal elements play a contributory part in maintaining the shape of the jacket and constitute the concrete reinforcement of the structure after pouring of the concrete.

In accordance with another advantageous property of the invention, the device comprises a system for retaining the jacket in its folded state until it is unfolded in the erection area, and means for progressively releasing said retaining system.

Further properties of the invention will become apparent from the following description, reference being made to the accompanying drawings which are given by way of example and not by way of limitation, and in which:

FIG. 1 is a general view of the device employed for building a vertical structure of the tower" type and in the transportation position;

FIG. 2 is a diagrammatic and fragmentary sectional view of the wall of a flexible and reinforced jacket;

FIG. 3 is a diagrammatic and fragmentary sectional view of the jacket shown in FIG. 2 and folded-back so as to form uniform pleats;

FIG. 4 is a sectional view in greater detail showing the attachment of an integrated reinforcement element to the wall of the same jacket, said element being joined to an element which is external to said wall;

FIG. 5 is a diagrammatic sectional view in a transverse plane with respect to the plane of FIG. 4 and showing a mode of attachment which is similar but carried out by means of a quick-clamping bracket;

FIG. 6 is a sectional view showing the attachment of a filling-pipe coupling;

FIG. 7 shows the device of FIG. I at the beginning of the operation in which the folded jacket has already been lowered;

FIG. 8 is a diagrammatic and fragmentary sectional view of the jacket of FIG. 7;

FIGS. 9 and 10 are diagrams of a tie-bracket of the jacket-retaining system of FIG. 8;

FIG. II is an alternative form of FIG. 8 with a massive base;

FIGS. 12 and I3 show diagrammatically alternative designs of the retaining system of FIG. 9;

FIG. 14 follows FIG. 8 after releasing of the retaining tie-brackets of the first jacket section and at the time of commencement of lowering of the supporting cables;

FIG. I5 follows FIG. 7 and shows the jacket which is in the course of being lowered;

FIG. 16 is an overhead plan view of the workshopvessel which is employed for the assembly of the jacket;

FIG. 17 follows FIG. I5 and shows the jacket in the fully lowered position;

FIG. 18 is a diagrammatic and fragmentary overhead plan view of the reinforcement system of the doublewalled jacket of FIG. 17;

FIG. 19 is a diagrammatic and fragmentary sectional view in perspective showing the jacket of FIGS. 17 and I8 and showing the constructional detail of the reinforcement elements and tie-brackets;

FIG. 20 is a transverse sectional view of a doublewalled reinforced jacket which is employed in the construction of a hollow horizontal structure such as a tunnel;

FIGS. 21 and 22 are diagrams in side elevation and showing the structure of the jacket of FIG. 20;

FIG. 23 is a diagrammatic sectional view of the mode of coupling of two sections such as those shown in FIGS. 20 to 22;

FIG. 24 is a diagrammatic part-sectional end view of the jacket of FIG. 20 after concreting;

FIG. 25 shows the floating craft which is employed for transportation and commencement of the installation of the jacket shown in FIG. 20;

FIG. 26 shows the substitution of a concreting unit for the supporting unit shown in FIG. 25;

FIG. 27 shows the concreting operation which is in progress on the jacket shown in FIG. 20;

FIG. 28 is a diagrammatic sectional view in the state of completion of the main construction, of a structure which is formed with the jacket of FIG. 20;

FIG. 29 is a diagrammatic general view of the complete system for laying a jacket of substantial length and consisting of coupled sections;

FIG. 30 is a diagram of the device for coupling two contiguous jackets in accordance with the constructional detail shown in FIG. 23;

FIG. 3] completes the lower portion of FIG. 28 and is a sectional view showing the structure formed by means of the jacket of FIG. 20 after completion of the main internal finishing operations.

For the construction of an immersed structure of the tower" type, the invention is directed to the installation of a structure as shown in FIG. I and essentially comprising a flexible jacket 1 carried by a workshopvessel 2 which is brought into position by any suitable means (not shown) and placed directly above the positioning area at a predetermined height above the underwater bed 3 which is assumed to provide a sufficiently firm foundation having an acceptable profile or which has been suitably excavated and prepared.

As shown in FIGS. 2. 3, I7, the jacket I comprises an external wall 6 and an internal wall 6a formed of flexible and leak-tight material such as natural or synthetic elastomer or polymer, for example. It is possible in particular to employ a rubberized fabric reinforced by either solid or hollow strengthening members 5. The material of the jacket wall must closely fit round the strengthening members. Said wall must be capable of being readily welded or vulcanized and of withstanding the pressure difference resulting from the difference in density or in pressure head between the external water and the internal liquid. Said material must withstand the thrust exerted by the fresh concrete and must finally have the necessary flexibility to admit of bending without breaking.

A jacket of this type can be prepared from uniform bands which are cut to size on a die-plate in order to produce the desired final volume. The linear seams (not shown) between adjacent elements are formed by any known means such as sewing, gluing, vulcanization. a reinforcing strip being added if necessary.

In one advantageous embodiment of the invention, the jacket is prepared by the so-called cocoonformation" process. To this end, a removable lightweight frame is constructed, there being sprayed onto said frame a first network of plastic filaments formed of material which dries or polymerizes fairly rapidly while remaining flexible. The fibers which are thus deposited in several layers if necessary have a high tensile strength and serve to produce appreciably enhanced resistance of the flexible and dense plastic material with which said fibers are subsequently coated also by spraying.

The passes of deposition of fibers and spraying of plastic coating can thus be performed in alternate sequence so as to result finally in a composite and flexible fabric having high strength. The thickness of the fabric can be adjusted according to requirements by successive passes which serve to deposit each time a fibrous network or a plastic coating having excellent mutual adhesion and excellent adhesion with respect to other elements composed of or coated with similar materials. This method is of particular interest for providing a connection between the wall of the jacket 6 and its integrated reinforcement system 5, for the fabrication of the strengthening members 10, and for any repair work which may prove necessary (see FIG. 4).

Once the jacket has been fabricated in the manner indicated in the foregoing, the lightweight frame which has served as a supporting stand for the assembly of bands or the cocoon-formation of the walls can be dis assembled and withdrawn.

It proves highly advantageous in practice to form a reinforced jacket, especially in the case of a jacket of the type shown in FIG. I. A reinforcement system composed of lightweight and sufficiently rigid elements greatly facilitates the fabrication, transportation and installation of the jacket. Relatively accurate and complex enclosed spaces can also be achieved by means of a reinforcement system of this type whereas unstiffened walls result in spaces which are limited to round bodies of very nearly spherical shape unless special precau tions are taken.

In order to form a reinforced jacket (as shown in FIG. 2), lightweight and rigid strengthening members 5 are encased in the wall 6 of the jacket or securely attached to said wall by bonding with addition of a reinforcing strip if necessary. The arrangement of the reinforcement is clearly dependent on the shape of the casting space which it is desired to form. The lightweight and relatively rigid members 5 of said reinforcement system can be made of metallic tubes which are suitably shaped and interassembled by different methods (see FIG. 4). It is also possible to make use ofelongated components, tubes or sectional shapes of plastic material reinforced with glass fibers or the like.

In addition to said strengthening members 5 which are integrated in the jacket wall 6, the invention makes provision for members 7 (shown in FIG. 4) which are connected to the strengthening members 5 by coupling distance-pieces 5b and so arranged as to be subsequently embedded in the concrete, thereby serving to increase the strength of this latter. In the case of metallic members 5, 5b, the connections can be made by welding. for example.

In the present invention. the flexible and leak-tight wall 6 (as shown in FIG. 2) is intended to be shaped prior to pouring of the concrete as a result of the pressure of the liquid ballast introduced into the casting space 40 within the interior of the jacket I. Said liquid ballast advantageously consists of a fluid medium hav ing a mean density which is higher than that of the sur rounding water. For example, advantageous use can be made of a slurry consisting of a suspension of clay or bentonite in water or alternatively any aqueous mixture containing granular particles. spherules or beads of plastic material so as to obtain a medium having a density which can be adjusted between predetermined lim- ".5.

The liquid ballast within the casting space 40 has the effect of displacing the flexible wall 6 of the jacket I both downwards and outwards. In order to increase the weight of the jacket and to assist the unfolding of this latter the liquid ballast can also be formed by directly employing the water of the surrounding medium and even sea water if the concrete employed is compatible with this latter. The advantage of these less elaborate liquid ballasts lies in their low cost price and also in the fact that they can be discharged directly to the exterior. In order to obtain the desired overpressure on the walls of the immersed jacket. it may prove sufficient to maintain within said jacket a predetermined excess of level of the liquid ballast with respect to the level of the external ambient medium.

The bulges thus formed in the wall 6 between the strengthening members 5 have the effect of maintaining said members in a substantially constant relative position. The general surface of the jacket 1 is thus subjected over its entire area to a uniform tension which maintains the shape of the jacket. Moreover, the profile of said bulges which constitute a characteristic feature of the invention is reproduced on the completed structure. This confers a number of different advantages on the structure, especially by enhancing the strength of any fills, embankments or adjacent structures.

In one advantageous embodiment of the invention shown in FIG. 4, the members 5 of the integrated reinforcement system and the coupling member 5b are constituted by metallic tubes previously coated with a sheath 8 of plastic material. Said plastic sheath 8 is chosen so as to have good bonding or gluing compatibility with the material of the jacket wall 6. A strengthening element 10 having a base of plastic material which is compatible with the materials of the jacket 6 and of the sheath 8 is applied on the contiguous surfaces in order to provide a stronger connection.

Similarly, it is also possible to provide ties which pass through the jacket wall 6 in leak-tight manner and are securely attached to different members 5 of the reinforcement system. In this case. the similar coupling members 5b traverse the wall 6 through a hole which is subsequently rendered leak-tight by means of a strengthening element which is similar to the element I0. As will be explained hereinafter with reference to FIGS. 8 and 9, the aforesaid coupling members which pass through the wall serve in particular to provide different fastening means for maintaining or supporting the wall 6 of the jacket I. The strengthening elements such as the element 10 must have high strength as well as good adhesion and are applied by gluing or bonding, or alternatively by spraying with a complex of fibers and fluid material such as to acquire a consistency which is comparable with that of the material of the walls 6. Leak-tightness of the enclosed casting space 40 is ensured by means of said strengthening elements and is an important condition which must be satisfied for the good performance of the method.

As shown in FIGS. 1, 2, 4, said jacket system permits a wide range of different forms of construction as stated earlier, namely massive structures if a singlewalled jacket 6 is employed and hollow structures if the jacket has a double wall as is shown by way of example in FIG. 17. The closed space 40 which is formed between the external wall 6 and internal wall 6a corresponds in this case to the casting space of the structure.

In order to form vertical structures of the tower type having a cross-section of circular shape, for example, it is an advantage to arrange the jacket 1 (shown in FIG. 1) and its reinforcement system 5 (shown in FIGS. 2 and 4) in such a manner that these latter can be brought into position directly above the construction site 3 in the folded state corresponding to a small overall size.

To this end, the jacket 1 is reinforced and foldedback so as to form uniform and superposed pleats as shown in FIGS. 3, 8 and 9. Tie-brackets such as those designated by the reference 21 in FIG. 9 extend through the jacket wall 6 and are joined by welding, for example, to the parallel circular members of the reinforcement system 5. The tie-brackets 21, 22 shown in FIG. 8 are provided in a sufficiently large number in spaced relation along the periphery of the walls 6 and 6a of the jacket I to permit the release of said tiebrackets in successive series during the regular unfolding of the jacket. Each peripheral series of tie-brackets 2!, 22 corresponds to one of the horizontal sections of the jacket which are intended to be unfolded one after the other. This precaution makes it possible in particular to guard against any uncertainty in regard to the positions of the walls 6 and 6a during an unfolding operation which necessarily takes a fairly long time.

The constructional detail of the reinforcement system of the jacket 1 is shown in FIGS. I7, 18 and 19. Said reinforcement system is made up of circular members 5 and 5:: integrated with the walls 6 and 6a which are substantially parallel to each other and joined by means of spacer members 5b and 5b to other parallel circular members 7 and 7a which are external to the walls 6 and 6a and serve as steel reinforcement for the concrete within the casting space 40. The tie-brackets 21, 22 extend in leak-tight manner through the walls 6 and 6a and are secured by welding, for example, to a certain number of circular members and 5a which are braced by spacer rods 50. Said spacer rods also serve to maintain in a constant relative position the circular members 7 and 7a, the circular members 5 and 5a, and the walls 6 and 6a of the jacket I.

Each series of tie-brackets 21, 22 (as shown in FIGS. 8 and I9) corresponds to one edge of the jacket I for the progressive unfolding of said jacket. The tiebrackets 21, 22 are rigidly fixed respectively to the circular members 5, 5a of the integrated reinforcement system of the walls 6, 60.

Each tie-bracket 21, 22 aforesaid is provided with a drilled hole such as the hole which is designated by the reference 21a in FIGS. 9 and I0 and through which is passed an externally threaded sleeve 43 having two symmetrical portions separated by a diametral plane. The sleeve 43 is screwed into a nut 43a and connected by means of a cross-pin 43c to a rod 42 which can be set in rotational motion so as to drive the sleeve 43. The nut 43a is secured against rotation by the dowel-pin 43!) which is fixed in the tie-bracket 21. Springs 432 are compressed between the rod 42 and each of the two portions of the sleeve 43 in order to release this latter from the cross-pin 430 when the nut 43a is no longer engaged with the threads of the sleeve 43.

In order to release the tie-bracket 21 (as shown in FIGS. 8, 9, I0, 14) the rod 42 is caused to rotate by means of the mechanism 41 until the nut 43a is caused to escape, thereby ejecting the two halves of the sleeve 43 under the action of the springs 43c. In order that the series of tie-brackets Zip, 211 2lz may be released in succession after the first series 21a, the sleeves 43 of these series of tie-brackets have an increasing number of threades at a rate, for example, of two or three additional threads from one series to the next (as shown in FIG. 14). By virtue of this arrangement, it is thus unnecessary to work underwater in order to free the tiebrackets during unfolding of the jacket.

As shown in particular in FIGS. 8 and IS, the base of the structure is formed in accordance with the desired profile by means of a special section 25 of the jacket I. This section is provided with a rigid structural framework 26 which cannot be folded back and comprises upright members, cross-members and diagonal struts 27, 27a, 27b within the interior of the casting space 40. This internal structural framework is connected to the integrated reinforcement system of the wall 60 of said special section 25. Moreover, said framework serves as a support for the coupling members 31 which pass through the wall 60 in leaktight manner and hold the fastening elements to which suspension cables 49 are intended to be attached so as to permit retention and controlled lowering of the jacket 1.

For the purpose of loading and utilization (see FIGS. 1, 7, l5, l6, [7), the jacket I is retained by said suspension cables 49 which are connected to the fastening elements 30 of the bottom section. The suspension cables 49 are attached to pulley-blocks l5 and these latter are secured to a ring'beam 19 held by the horizontal support structure 2e of a workshop vessel 2 having two hulls 2a. 2b. Said hulls are mounted in spaced relation 8 by cross-beams 46 which support an operating platform 46a.

The relative spacing of the halls 2a, 2b, as well as the cross-beam 46 and the arrangement of the operating floor 46a which is open in the entire central portion thereof permit the vertical transfer of the jacket for loading and subsequent lowering. In the transportation position shown in FIG. 1, the bottom section 25 of the folded-back jacket rests on the cross-beam 46 by means of a temporary structure which is not shown in the drawings. The operating floor 46a is also employed for the attachment of units 4|, 4Iu which control the release of the jacket-retaining system (as shown in FIGS. 8, l4, 16). Finally, said floor 460 is used for operations which involve preparation and utilization of the jacket I and which can all be carried out above the water.

In order to bring the jacket I in directly overhead relation to the construction site 3, the workshop vessel 2 (shown in FIGS. 1 and 7) is propelled and maintained in a fixed position by any known means such as tugs. independent motors with orientable screw-propellers, fixed moorings.

The workshop vessel 2 is also fitted with special means for the utilization of the jacket. The vessel is provided in particular with means l5, 19, 49 for supporting and lowering the jacket I. The vessel also has means 42, 43, 52, 53 for filling with liquid ballast and with concrete and designed to operate in association with external means (factory barges. tanker barges) such as those designated by the references 41 and SI in FIG. 15. Means are also provided on the vessel for actuating the device which serves to support the jacket I as hereinabove described in connection with FIGS. 8, 9, 10.

In one advantageous embodiment of the invention which is illustrated in FIGS. 2, l5, 16, the supporting and lowering means comprise a series of pulley-blocks 15, the movable pulleys 16 of which are connected to the fastening elements 30 of the jacket by means of the suspension cables 49. The stationary pulleys 18 are rigidly fixed to the ringbeam 19 which is carried by the workshop vessel 2. As shown in FIGS. 1, 2, l5, 16, the contour of the ring-beam 19 corresponds substantially to the contour of the jacket I. The fastening elements are disposed at uniform intervals along the periphery so as to support the bottom section 25 of the jacket 1 on the same side as the external wall 6 and on the same side as the internal wall 6a as shown in FIGS. 2, 8, 15.

The mechanisms for driving the winches (not shown) of said pulleyblocks 15 are centralized and provided with adjusting means in order to permit lowering of the jacket I in uniform motion at a sufficiently low speed to prevent any inertial effects. For example, said winches can be designed to perform simultaneous step-by-step operations in known manner, each step being intended to correspond to a displacement of a few centimeters.

Before proceeding with the progressive immersion and unfolding of the jacket, provision is first made for an initial step (as shown in FIG. 7) which consists in lowering the complete jacket I in the folded state by operating the pulley-blocks 15 to which the fastening elements 30 are attached until the top edge of the jacket reaches the level of the operating floor 46a which is carried above water level by the workshop vessel 2 (as shown in FIG. 16). The top edge of the jacket I is fixed on the operating floor 46a prior to unfolding. Said floor thus facilitates all the operations which will now be described hereinafter.

In order to permit lowering of the jacket 1 into the water as shown in FIG. 7 and in order to initiate unfolding of said jacket in accordance with the invention, the casting space 40 is filled with liquid ballast, thereby removing the buoyancy of said space and exerting a slight overpressure on the walls 6, 60 (shown in FIG. IS) with respect to the exterior. In order to carry out this filling operation. the workshop vessel 2 has a pumping set 42 and pipes 43, 44, 45 for discharging into the casting space 40 the liquid ballast which is supplied by a tanker barge 41.

As mentioned earlier, the liquid ballast can advantageously consist of an aqueous suspension of bentonite, the density of which is modified in accordance with the requirements of the operation. This slurry has several important advantages. In the first place, said slurry does not have any tendency to mix with the fresh concrete and to dilute this latter but can be permitted to remain with the concrete without any difficulty. A further effect of the slurry is to deposit a crust of pasty consistency on the walls of the jacket 1 and this crust can provide a remedy for certain local defects in leaktightness.

In the case under consideration (FIG. I7) in which the structure to be formed is intended to project above the surface of the water, the jacket I has an open top and the liquid ballast can readily be poured into this latter by means of a downwardly-curved pipe 45 carried by the operating floor 460 as shown in FIGS. and 16. The level of the liquid ballast within the casting space 40 is adjusted with respect to the level of the water outside the jacket, depending on the density of the liquid ballast and the desired value of overpressure within the jacket 1.

By continuing to lower the suspension cables 49 which support the fastening elements 30, the bottom section of the jacket 1 moves to a greater depth underwater. The operation of the pulley-blocks 15 is coordinated and carried out in step-by-step motion. This progressive lowering of the fastening elements 30 initiates the unfolding of the pleats of the external wall 6 and of the internal wall 6a (shown in FIG. 8) beneath the tiebrackets 2ln and 22n.

When this first section of free pleats has unfolded to a sufficient extent as shown in FIGS. 8 and 14, action is produced on the rods 42 by means of the rotational control units 4] which are carried by the operating floor 46a. The coordinated operation of said units serves to release the first series of tie-brackets 2ln, 22n as shown in FIG. 14 and to continue the lowering of the jacket I and uniform unfolding of this latter. The successive release of the series of tie-brackets 21p, 22p and then Zlq, 22q corresponds each time to the initial unfolding of a further section of the jacket 1 whilst the fastening elements 30 continue to be lowered as required by the pulley-blocks 15 which are attached to the suspension cables 49.

Having come into contact with the bottom or underwater bed 3 as shown in FIG. I7, the bottom section 25 of the jacket I rests on said bed in a stable manner under the action of the weight of the liquid ballast contained in the casting space 40. The flexible jacket and its flexible reinforcement system closely conform to the irregularities of the bed 3. The bearing face of the cast concrete will finally be in uniform contact with the bed 3 and even in a slightly oblique manner without affecting the verticality of the walls 6, 6a of the casting space 40 since these walls are suspended at the top portion of the jacket which remains attached to the operating floor 460 until completion of the construction work.

The suspension cables 49 can then be detached from the fastening elements 30 of the bottom section 25 of the jacket by any known means (divers or hydraulically operated trip-hooks or alternatively electrically fired low-energy explosive bolts). It is also an easy matter to connect the flexible leads or piping to the suspension cables 49 or to the jacket walls 6 progressively as the jacket moves downwards underwater (see FIGS. 15 and 17).

Before commencement of the concreting operation. complementary concrete reinforcement elements I49 are introduced within the jacket as shown in FIGS. l7. l8, 19. said reinforcement elements being provided with guides 47 which are adapted to slide along the circular reinforcement members 7 and 7a and over the spacer rods 5d. Said complementary reinforcement elements I49 are also provided with positioning members 48 which are used for accurate stacking of said elements progressively as these latter are introduced within the casting space 40 by means of pulley-blocks suspended from the ring-beam l9.

Pouring of the concrete into the casting space 40 is then performed as shown in FIG. 17 by the pumping means 52 and the supply pipes 53, 55. The concrete which is delivered by a barge S1 is not poured directly into the casting space 40 which is full of liquid ballast but introduced by means of a vertical pipe 56 which is suspended from the ring-beam l9 and the lower end 57 of which has its opening substantially at the bottom of the casting space. The vertical pipe 56 passes, for example, into one of the free vertical spaces within the interior of the elements I49, as shown in FIG. 18.

Progressively as the filling and spreading of concrete take place, the lower end 57 of the pipe aforesaid is moved upwards in order to maintain this latter constantly at a short distance above the level of spreading of the concrete. This prevents any irregularity in the mixture of aggregates of different sizes which constitute the concrete as could otherwise be the case if the concrete were permitted to fall freely into a substantial thickness of liquid ballast (phenomenon known as "segregation).

In the case of a structure of the type shown in FIG. 17 which has substantial dimensions and a diameter of 20 meters, for example, pouring of the concrete cannot be performed at a single point. On the contrary, it is necessary to carry out this operation at several points by means ofa plurality of connecting-pipes 55 and vertical pipes 56. For reasons of clarity, only one connecting-pipe 55 and one pipe 56 are shown in FIG. 17. Moreover, it is frequently advantageous to employ different known methods for activating the setting of the concrete. Rapid solidification of this latter and minimized immobilization of the workshop vessel 2 are added to the other advantages of the invention.

As soon as the introduction of the concrete into the casting space has begun, the liquid ballast is recovered by means of a pipe such as 44, 45 as shown in FIG. 15

in order to return said ballast into the tanker barge 4] by means of a pump set 42. The flow motion is regulated so as to maintain the level within the jacket at a height such that the unfolding of the entire upper portion of the jacket remains satisfactory.

Once the concreting and simultaneous recovery of the liquid ballast have been completed, the concrete hardens progressively within the casting space 40. As soon as the hardness of the concrete is sufficient, the main construction work is completed. The workshop vessel 2 together with its lifting means 15 and operating floor 46a (shown in FIG. 16) continues to perform a useful function for the finishing operations which are primarily concerned with the upper portion of the structure.

The main advantages of the invention as hereinabove described with reference to the construction of a hollow structure of the tower type are as follows: by means of the invention. work can be performed entirely out of the water for the greater part of the main, construction and if necessary even for the final operations such as the detachment of the suspension cables 49 (FIG. 15) by the remote-control means hereinabove described.

This possibility of operating completely out of the water introduces a considerable improvement, especially in regard to working efficiency and safety of personnel and ease of handling operations.

A further considerable advantage lies in the fact that the immersed unit weights to be displaced, supported and lowered underwater are of a very low order by reason of the buoyancy of the casting space 40 (shown in FIG. 15) in which the filling with liquid ballast can be varied at will over a fairly wide range. The advantage remains substantial even in the case of a massive footing-block 35 (shown in FIG. 11) since the immersed unit weight of a mass of reinforced concrete in water is of the order of only 1.5 compared with 2.5 in air.

These features of the invention also play a part in reducing the time allotted for operations and the total cost of a construction project.

The particular profile of the walls of the completed structure in the form of convex segments in accordance with the profile of the unfolded jacket is also favorable to the general strength of the structure when this latter is placed either against other constructions or against an embankment.

The wall of the jacket 1 remains anchored to the concrete wall of the completed structure. Since the jacket wall is formed of high-strength plastic material and provided if necessary with a high-strength integrated reinforcement of rigid plastic material which may in turn be reinforced with glass fibers, for example, said wall ensures that the concrete structure is effectively protected against the deleterious action of external agents. It is readily apparent that the nature, thickness, strength and type of anchoring of said wall may have been given special study if special conditions arise from the need for protection of the concrete.

The possible applications of the invention within the field of vertical structures vary over an extremely broad range. Apart from the constructions required for lighting and direction-marking in the sea or in rivers, the invention also makes it possible to construct bridge piers, quay or dam elements, reservoirs. Whether it is intended to build either massive or hollow structures, it is possible in each case to adapt the shape of the jacket to the desired contour and even to construct the jacket in a number of sections if necessary in order to obtain a wide range of different vertical profiles.

The construction of a hollow vertical structure having an upper portion which projects above the water level has been described in the foregoing by way of example of application of the invention. It is apparent, however, that the invention is not limited to this single example or to the different specific details which have been described in this connection but that many alternative fo rms of execution can be contemplated.

In particular, the invention is applicable to structures of very different shapes corresponding, for example, to elliptical, cruciform or L-shaped sections which can readily be reproduced and maintained by rigid elements ofa reinforcement system which is similar to that described earlier with reference to FIG. 19. Inasmuch as it is joined to the jacket walls, said reinforcement system always permits the possibility of folding the jacket 1 in a compact form for transportation and presentation on the work site by making use of tie-brackets which are remotely operated from the surface both for supporting and progressively unfolding said jacket.

An alternative method for assembling the elements of said reinforcement system consists in the use of quickclamping brackets 9 (as shown in FIG. 5) which are similar to those employed in metallic scaffolding. The uncovered metallic portions are given a complementary plastic sheathing which is similar to the pre iminary and normal sheathing 8 of the members 5, 5b In order to ensure maximum adhesion of the flexible wall 6 and of the plastic reinforcement 10 to all these elements. The assembly components 9 can also be formed of rigid plastic material.

The bottom section 25 of the jacket as described with reference to FIG. 8 can be constructed in a different manner. In the embodiment of FIG. I], the base of the structure is constituted by a prefabricated massive footing-block 35 which forms a ballast and isjoined in leaktight manner to the lower portion of the walls 6, 6a and is suspended from the ring-beam 19 (as shown in FIG. 7) by means of cables 36 which are similar to the suspension cables 49. As illustrated in FIG. 11, said cables 36 are attached to the base of the footing-block 35 by means of special fastening units 37 which extend through the casting space 40. Depending on the weight to be supported, provision is made for a number of fastening members which are spaced at equal intervals around the periphery of the footing-block 35.

The cables 36 are maintained under tension throughout the concrete-hardening stage. Tensioning mandrels are then placed in position on the top face of the mass of hardened concrete. Said mandrels are similar to the fastening unit 37 and comprise a bearing plate and clamps for attachment to the cables 36. The mandrels and bearing plates have previously been passed over the cables 36 or are constructed in a number of removable sections in order that they can be placed on the cables which have already been tensioned. The final tension applied by each cable 36 within the mass of concrete can thus be adjusted; the top portions of said cables 36 can then be cut-off above the concrete.

In another alternative form of construction, the jacket can be subjected to a fairly powerful unfolding action even with liquid ballasts of low relative density by employing a jacket which is either closed or temporarily sealed-off at the top in order to exert a sufficiently high pressure therein, this being achieved by introducing the liquid ballast under pressure by means of 

1. A method for building at least partiaLly immersed structures by pouring concrete or any like hardenable material, wherein a flexible and leak-tight jacket is placed in position at the intended location, wherein at least part of the internal space of said jacket is filled with a liquid ballast having the design function of applying to the jacket walls a pressure which is higher than the ambient hydrostatic pressure, wherein the internal space of the jacket which is thus filled corresponds substantially to the casting space of the structure to be built, and wherein the concrete or like hardenable material is then poured into the jacket while discharging the liquid ballast which had been present therein.
 2. A method according to claim 1 as applicable to the construction of massive structures, wherein a single-walled jacket is employed.
 3. A method according to claim 1, wherein a reinforcement system comprising both elements which are integrated with the jacket wall and other elements located within the casting space and intended to constitute the concrete reinforcement are placed in position within said jacket.
 4. A method according to claim 1, wherein the jacket wall is formed by spraying a plastic material in the fluid state onto a framework and causing the subsequent hardening of said material.
 5. A method according to claim 4, wherein the spraying is carried out in several successive passes and at least one of said passes consists in depositing fibers of substantial length which are then embedded in the jacket wall.
 6. A method according to claim 1 as applicable to the construction of hollow structures such as tunnels or towers, wherein a double-walled jacket is employed, the space formed between the two walls of the jacket being such as to correspond substantially to the casting space of the structure to be built.
 7. A method according to any one of claim 1, wherein the liquid ballast consists of a slurry such as an aqueous suspension of bentonite, an aqueous suspension of clay or of beads of plastic materiial.
 8. A method according to claim 1, wherein the liquid ballast is of the same nature as the surrounding medium and wherein the level of filling with liquid ballast within the jacket is maintained above the free surface of the ambient liquid.
 9. A method according to claim 1 and primarily intended for the construction of vertical structures of the tower type, wherein the jacket is brought into position above the construction site in the folded state and wherein progressive unfolding of the jacket is carried out until the final casting volume is obtained.
 10. A method according to claim 9, wherein progressive unfolding of the jacket is carried out in successive sections by subjecting the lower portion of the jacket to a tractive effort while retaining the remainder of said jacket and wherein the sections of the jacket located at the base of the portion which still remains in the folded state are released in turn.
 11. A method according to claim 10, wherein progressive unfolding of the jacket is initiated by filling said jacket with the liquid ballast.
 12. A method according to claim 11, wherein progressive unfolding of the jacket is carried out by means of a ballast attached to the lower portion of the jacket and wherein said ballast is suspended by means of ties which pass within the interior of the closed space of said jacket and serve to control the lowering of the ballast from the surface.
 13. A method according to claim 12, wherein the ballast is suspended by means of cables maintained under tension throughout the operation and until final hardening of the concrete which is poured into the jacket and surrounds said cables.
 14. A method according to claim 9, wherein the reinforcement system is unfolded at the same time as the jacket and wherein said reinforcement system is completed by concrete reinforcement elements which are introduced into the casting space after unfolding of said jacket.
 15. A method according to claim 1 and applicable to the construction of horizOntal structures of substantial length such as tunnels, wherein the reinforced jacket is supported in order to be presented in parallel relation to the surface of the liquid medium, wherein one end of the jacket is progressively lowered underwater until said jacket rests on the underwater bed, the connecting section between the portion which is supported at the surface and the portion which rests on the bed being maintained at an oblique angle, and wherein the reinforced jacket is positioned on the bed while ensuring the progression of said oblique connecting section in the direction of laying.
 16. A method according to claim 15, wherein the jacket and jacket reinforcement system are designed in sections which can be coupled to each other on the construction site.
 17. A method according to claim 1, wherein the concrete is poured from the surface by means of a substantially vertical pipe and wherein the lower end of said pipe is progressively displaced upwards as the filling of the jacket proceeds, said upward displacement being regulated so as to ensure that said lower extremity remains in the vicinity of the level of spreading of the concrete.
 18. In a device for the construction of at least partly immersed concrete structures, comprising a jacket having two flexible walls which are substantially parallel to each other in the service position and thus define a moulding volume, and reinforcing elements between said two walls; the improvement wherein reinforcing elements are also provided for each wall and embedded within said wall, means for connecting the reinforcing elements between the walls with the reinforcing elements of each wall and for connecting opposite reinforcing elements of said two walls, and for transporting the jacket and installation of said jacket on the construction site, at least one floating equipment unit having jacket-supporting means and jacket-lowering means, and pumping means for the flow motions of liquid ballast and for pouring concrete and pipes connectable to said pumping means.
 19. In a device for the construction of at least partly immersed concrete structures, comprising a jacket having two flexible walls which are substantially parallel to each other in the service position and thus define a moulding volume, and reinforcing elements between said two walls; the improvement wherein reinforcing elements are also provided for each wall and embedded within said wall, and means for connecting the reinforcing elements between the walls with the reinforcing elements of each wall and for connecting opposite reinforcing elements of said two walls, the jacket having suspension members rigidly fixed to the jacket reinforcement system and connectable to external suspension and lowering means, said suspension members being external to the jacket wall and joined to said reinforcement system by connecting members which pass through said jacket wall in leaktight manner.
 20. In a device for the construction of at least partly immersed concrete structures, comprising a jacket having two flexible walls which are substantially parallel to each other in the service position and thus define a moulding volume, and reinforcing elements between said two walls; the improvement wherein reinforcing elements are also provided for each wall and embedded within said wall, means for connecting the reinforcing elements between the walls with the reinforcing elements of each wall and for connecting opposite reinforcing elements of said two walls, the jacket having a supporting system comprising series of tie-brackets for retaining the jacket in the folded state until unfolding thereof, each series of tie-brackets retaining one section of said jacket, and means for releasing the tiebrackets of each series.
 21. In a device for the construction of at least partly immersed concrete structures, comprising a jacket having two flexible walls which are substantially parallel to each other in the service position and thus define a moulding volume, and reinforCing elements between said two walls; the improvement wherein reinforcing elements are also provided for each wall and embedded within said wall, means for connecting the reinforcing elements between the walls with the reinforcing elements of each wall and for connecting opposite reinforcing elements of said two walls, concrete reinforcement elements which are introduced within the casting space after positioning of the jacket, said elements having guides slidably mounted on the reinforcement system which is rigidly fixed to the jacket, and positioning means so arranged as to ensure that said concrete reinforcement elements are placed in position with respect to the reinforcement system.
 22. A device according to claim 19, wherein the floating equipment unit carries a ring-shaped structure having a contour which corresponds substantially to that of the structure to be built, and wherein said ring-shaped structure supports at least part of the means for application of the jacket.
 23. In a device for the construction of at least partly immersed concrete structures, comprising a jacket having two flexible walls which are substantially parallel to each other in the service position and thus define a moulding volume, and reinforcing elements between said two walls; the improvement wherein reinforcing elements are also provided for each wall and embedded within said wall, and means for connecting the reinforcing elements between the walls with the reinforcing elements of each wall and for connecting opposite reinforcing elements of said two walls, the jacket having a number of series of couplings spaced at uniform intervals in the direction of the length of the jacket for liquid ballast pipes and concrete supply pipes, each connecting unit for the concrete supply pipes being attached to the summit of a protuberance formed on the jacket, said protuberance having a flared bottom portion and a summit which is located at least at the same height as the top level of the central portion of the normal casting section.
 24. In a device for the construction of at least partly immersed concrete structures, comprising a jacket having two flexible walls which are substantially parallel to each other in the service position and thus define a moulding volume, and reinforcing elements between said two walls; the improvement wherein reinforcing elements are also provided for each wall and embedded within said wall, means for connecting the reinforcing elements between the walls with the reinforcing elements of each wall and for connecting opposite reinforcing elements of said two walls, the jacket being formed in sections which can be coupled to each other, the end faces of each section being fitted with coupling-band units having strengthening members rigidly fixed to the reinforcement system and means for establishing a connection with the corresponding strengthening members of the coupling-band units of adjacent sections.
 25. A device according to claim 24, comprising a series of floating units having means for bringing the reinforced jacket sections into position above the construction site, means for coupling said jacket sections to each other, means for progressively lowering the coupled sections and filling them with liquid ballast, and means for concreting the immersed section. 